1. Field of the Invention
The present invention relates in general to a tamper-evident container closure and a container neck structure. More particularly, the present invention relates to a closure having a foil disc. The closure is applied to the neck with an axial downward force without rotation relative to the container, with the foil disc sealing the neck of the container. After the tamper-evident feature of the closure is removed, the cap may be screwed onto and off the container as a reclosure cap.
2. Description of the Related Art
Many closure systems include foil liner seals to cover the neck opening, providing evidence of tampering and preserving the freshness of the product. The commercially available foil seals usually have an adhesive substance applied on one surface of the seal. When applied to the neck, the adhesive-coated surface is placed in contact with the neck structure surrounding the opening. The foil seal discs are generally adhered to the container by induction heating or other means. The foil disc is typically initially inserted into the cap and sealed to the neck of the container during the capping process, facilitating installation of the liner seal.
Many of the available foil liner seals are formed with a tab which may be gripped by the consumer to remove the seal and open the container. As is shown in U.S. Pat. No. 4,739,891, the tab is folded back across the main body of the foil disc when inserted into the closure. A paper liner preferably separates the foil disc from the interior of the cap, preventing adherence of the tab to the underside of the cap when the foil disc is sealed to the neck. Without the paper liner, the tab bonds to the cap and may pull the foil disc from the neck when the cap is initially opened. The premature breaking of the seal provides a false indication of tampering.
The snap-on, screw-off structures available in the prior art are of two general types-those having thread engagement as initially applied, and those without initial thread engagement. Examples of closure systems having no-thread initial engagement are those taught by U.S. Patent No. 4,561,553 to Crisci, and U.S. Pat. No. 4,946,055 to Towns et al. The no-thread initial engagement system has the major advantages of being simple to manufacture and apply and of achieving good re-seal on reclosure through the thread torque. However, using a foil disc initially inserted in the cap with this system is impractical. Furthermore, the requirement of twisting the closure relative to the neck after the container is initially opened by a lifting motion is confusing to the consumer.
Systems having partial to full thread engagement on initial application have several advantages over the no-thread system, including the ability to effectively use a foil disc to seal the neck of the container. Consumer confusion is also eliminated, since the cap is initially removed from the container by twisting. However, the initial thread engagement systems do not offer the manufacturing and application advantages available with the no-thread system. With some systems, the closure must be twisted relative to the container at some point during the application process in order to seat the cap on the neck. An example of such a closure is shown in U.S. Pat. No. 4,625,875 to Carr. Other concepts, such as that taught by Miskin in the European Patent Specification No. 0 118 267 do not require orientation or twisting during application, and accommodate the inevitable closure height variation after application by employing an extended plug to seal against the inside bore of the container neck. The systems taught by Carr and Miskin both suffer from the requirement that the tamper evident band must be expanded over a restrictive container bead during the application process, which leads to difficulties. Furthermore, the bridges joining the removable band to the cap require mold slides for formation, a feature which greatly increases the cost and complexity of injection molding tooling.
Other systems available in the art include screw-on, screw-off structures which also offer the advantages of initial thread engagement and elimination of consumer confusion. An example of this type of closure is shown in U.S. Pat. No. 3,980,195 to Fillmore. The system taught by Fillmore includes a threaded, tamper-evident closure with a removable band. The interior of the removable band is formed with a one-way ratchet, which cooperates with projections formed on the neck to prevent unscrewing of the container. When the closure is initially twisted onto the container, the ratchet teeth slip over the projections on the neck. The application process used with the screw-on, screw-off systems is quite complex, since the cap must be turned or rotated relative to the container until the closure is fully seated. Furthermore, the frangible connections between the tamper-evident band and the closure must be sufficiently strong to prevent partial separation when the cap is twisted onto the container, increasing the costs of manufacture and the difficulty with which the band is removed from the container.
This invention provides a snap-on, screw-off system with partial or full thread initial engagement by reason of a unique thread design, a unique tamper-evident band and optional means for orienting the closure and container threads to achieve registration prior to straight axial application. A foil disc seals the neck opening of the container, providing evidence of tampering. The present invention offers considerable advantages over prior structures as is evident from the description of the related art and the following description of the invention.